Study On The Isolation,Identification And Insecticidal Activity Of Tenvermectin

Tenvermectins A and B are a kind of new 16-membered macrocyclic lactone antibiotics isolated from the fermentation broth of genetically engineered strain Streptomyces avermitilis MHJ1011.Compared with avermectins,ivermectins and milbemycins,tenvermectins were proved to possess better insecticidal property in the control of aphid,mite and other insect pests in agriculture and livestock parasite in animal husbandry.Due to the characteristics of broad spectrum,high efficiency and low toxicity,tenvermectins were considered to be a promising new generation of pesticides and veterinary drugs.The contents of this paper include the following sections: the isolation and structural elucidation of secondary metabolites of Streptomyces avermitilis MHJ1011,microbial transformation of tenvermectins and insecticidal activities of the obtained compounds.1.The isolation and structural elucidation of secondary metabolites of Streptomyces avermitilis MHJ1011.The 30 L fermentation broth of Streptomyces avermitilis MHJ1011 was filtered,and the mycelial cake was extracted by ethanol.By filtration,extraction and concentration,the 270 goily residue was obtained and then three metabolites were isolated with the help of silica gel,Sephadex LH-20 and reversed-phase HPLC methods.The structures of the three compounds were elucidated as analogs to tenvermectin on the basis of NMR,HRESIMS,IR and UV spectroscopic analysis.So they were named as tenvermectin C,tenvermectin D and tenvermectin E,respectively.2.Microbial transformation of tenvermectins A and B.We carried out the transformation study of tenvermectins A and B with eight microbial strains.Based on the TLC and HPLC profiles,two strains have the ability to transform tenvermectins and Saccharopolyspora erythraea ATCC 11635 possess higher transformation potential.So we examined the microbial conversion of tenvermectins A and B by Saccharopolyspora erythraea ATCC 11635.Finally,we obtained two new tenvermectin analogs by silica gel,Sephadex LH-20 and reversed-phase HPLC methods from the fermentation broth.The structures of the two transformation compounds were elucidated according to NMR,HRESIMS,IR and UV spectroscopic analysis.Consequently,both of the two transformation compounds were new and their structures were established as 4?-O-glucosyl tenvermectin A and 4?-O-glucosyl tenvermectin B,respectively.3.The insecticidal and acarcidal activity of the obtained new compounds.The nematocidal and acaricidal activity of tenvermectin C,tenvermectin D and tenvermectin E against Bursaphelenchus xylophilus and Tetranychus cinnabarinus,respectively,reared in the laboratory were evaluated.The bioassay results demonstrated that the LC₅₀ values of tenvermectin C and tenvermectin D against Bursaphelenchus xylophilus were 3.8156 and 4.1542 mg/L,respectively,while tenvermectin E almost have no nematocidal activity.The LC₅₀ values of tenvermectin C,tenvermectin D and tenvermectin E against Tetranychus cinnabarinus were 0.0110,0.0105 and 0.0837 mg/L,respectively.The insecticidal and acaricidal activity of 4?-O-glucosyl tenvermectins A and B against Bursaphelenchus xylophilus,Plutella xylostella,Algedomia coclesalis and Tetranychus cinnabarinus,respectively,reared in the laboratory were also evaluated.The bioassay results demonstrated that the LC₅₀ values of the two bioconversion products,4?-O-glucosyl tenvermectins A and B,against Bursaphelenchus xylophilus were 6.7984 and 5.7980 mg/L,respectively.The LC₅₀ values against Plutella xylostella were 0.0534×10³ and 0.0349×10³ mg/L,respectively.The LC₅₀ values against Algedomia coclesalis were 7.2568 and 6.1104 mg/L,respectively.The LC₅₀ values against Tetranychus cinnabarinus were 0.0156 and 0.0113 mg/L,respectively.